## Who is the liar but he who denies that Jesus is the Christ? ##
John used a rhetorical question to emphasize who the liars are. It could be translated as a question with an answer: "Who is the liar? It is anyone who denies that Jesus is the Christ." (See: [[rc://en/ta/man/translate/figs-rquestion]])
## denies that Jesus is the Christ ##
"refuses to say that Jesus is the Christ" or "says that Jesus is not the Christ"
## denies the Father and the Son ##
This can be translated as "refuses to say the truth about the Father and the Son" or "rejects the Father and the Son."